Airbus A321-231, G-MIDJ
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Discussion
Thunderstorm activity was only depicted on the forecast Significant Weather charts for the route to
Cyprus as 'ISOL EMBD CB' over the Alps. This was noted by the flight crew and at the pre-flight
briefing the commander warned the cabin crew of the possibility of turbulence occurring during that
part of the flight. The line of CB activity associated with the cold front lying across Hungary was not
depicted on the chart as its intensity was forecast as not meeting the 'EMBD' or 'OCNL CB' criteria.
The departure from Cyprus was flown in clear conditions where the weather radar was only used to
monitor the cloud building up over the northern part of the island and over the Turkish mainland to
the right of the intended track. This weather was clearly depicted on the chart and the commander
visually assessed the tops of the clouds to be at approximately FL280. Thereafter the flight was
generally conducted in clear conditions above some ISOL CU with the flight crew being able to
visually assess the weather ahead of the aircraft. The weather radar, when selected, was displayed on
the ND being used by the PF and was visible to the commander.
As the flight progressed neither pilot adjusted the radar tilt leaving it selected 2º to 3º down. They
were satisfied that the weather returns to the right and minor returns to the left of track posed no
significant threat to the aircraft and thus the radar was selected OFF.
The weather radar has the limitation that ice crystals, dry hail and dry snow above 30,000 feet will
only give small reflections. A pilot must therefore rely on vertical scanning of a storm cell, using the
tilt facility to direct the radar beam, in order to detect adverse weather. This was not the technique
being used when the crew observed what they interpreted as minor returns before they deselected the
radar. They thus entered an area of significant turbulence and hail without warning.
As a result the aircraft suffered significant damage to the airframe and some of the flight deck
windows. The only damage visible to the crew however was that evident on the flight deck. Neither
the commander nor the FO left the flight deck to examine the wings or engine intakes from the
passenger cabin windows. Had they done so it is unlikely that they would have been able to
appreciate the level of damage to the aircraft as the small but numerous indentations left by the hail
stones were not visible from the cabin. Furthermore, the areas where the hail had penetrated the
aircraft skin were not visible from within the aircraft.
The manufacturer's opinion was sought regarding whether or not a diversion should have been carried
out given the level of damage caused to the aircraft. They believed that the design of the structure,
based on certification requirements and design specifications, was such that it absorbed the damage
and the aircraft remained in a safe condition.
The FMGS provided information on the fuel estimated to be on board when the aircraft arrived at its'
destination and any extra fuel available. When the aircraft descended and levelled at FL230 these
amounts were recalculated by the FMGS computer and should have remained constant for the
remainder of the flight. Any unexplained reduction of these amounts could have indicated
degradation in the aircraft's performance brought about by an increase in airframe drag caused by the
damage. This would have been of greater potential significance if the aircraft had been carrying out
an Extended Range Twinjet Operation (ETOPs).
The windscreen in front of the commander and the DV window on the FO's side were both damaged.
In the event, although the first officer carried out the landing and taxi to the stand, the commander still
had enough vision to park the aircraft. It is worthy of note that if the damage had been more
significant and the visibility through both front windscreens had been degraded the crew would still
have been able to have landed the aircraft using the autoland facility.
Finally, testing of the FDR showed that it correctly recorded when the weather radar was selected ON
or OFF. This recorded evidence however, is at variance with the recollection by the crew of when the
radar was being operated. It is of note that the FDR discreet, recording the status of the weather radar,
was only tested after significant disruption to, and reconnection of the aircraft avionics system.
Airbus A321-231, G-MIDJ
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Therefore because the reliability of the recorded evidence could be questioned the investigation
accepted the account of the events provided by the crew.
Airbus A321-231, G-MIDJ
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Conclusions
This serious incident occurred when the aircraft, initially cruising in VMC, entered an area of cirrus
　
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